1. Field of the Invention
This invention relates to a process for aralkylating alkylbenzenes with styrenes. It is more particularly concerned with a process for catalytically aralkylating alkylbenzenes by continuously feeding an alkylbenzene and a styrene to a catalyst layer filled with synthetic silica-alumina that has been subjected to calcination at temperature between 450.degree. C. and 600.degree. C.
2. Description of the Prior Art
Alkylation reactions between an alkylbenzene and an olefin which are the most important reactions in chemical industry find many uses. In cases where aromatic olefins such as styrene (termed styrenes hereinbelow) are employed as the olefin the reaction is called an "aralkylation" reaction. Non-condensed polycyclic aromatic hydrocarbon compounds from the aralkylation between an alkylbenzene and a styrene which have excellent properties in terms of compatibility, heat resistance, lubricity and electric properties are synthetic oil suitable for wide uses such as those as plasticizer, high-boiling solvent, heat medium, electric insulating oil, working oil and lubricant. The desired aralkylated alkylbenzenes that are the synthetic oil of desirable properties for these uses cannot be produced in a high yield due to liability of styrenes to be polymerized when one of the conventional alkylation catalyst is used.
As the heretofore disclosed aralkylation catalyst are mentioned concentrated sulfunic acid proposed in British Pat. No. 977,322 and acidic solid acids proposed in U.S. Pat. No. 3,069,478. The process with sulfuric acid, when operated on an industrial scale, requires not only high cost for the aftertreatment such as the water required for the neutralization to remove the catalyst after completion of the reaction but also means for preventing corrosion of the equipment as well as environmental pollution from the discharged water. On the other hand, prior art technique by the use of clay mineral catalysts such as acid clay represents batch processes of the catalytic reaction only.
It has been found that the synthetic silica-alumina containing from 7% to 15% alumina disclosed in U.S. Pat. No. 3,069,478 is unfitted in practice for use in the continuous process, owing to its short life, although, as described in detail in the patent specification, it is effective in the batch reaction.